"The whole approach has been to hit the Russians with a stick. They're pretty tough characters and whether we'd have done any better with a carrot, I don't know," he said.

"But the effect of just all this public berating of them - my feeling is they're going to sort of back into the corner and hit back.

"I think that was always going to be the reaction. Because what can Putin do? He can back down and lose face domestically and internationally or he can hit back. He's left in a very difficult situation."

He says he also doubts it is useful for Prime Minister Tony Abbott to label Russia a "bully".

"Right from the beginning we've been attacking the Russians. Now, Putin is far from perfect. He's a very authoritarian character. But it's a very complicated situation," Mr Hogue said.

"So public insults just doesn't seem to me to be getting anywhere, particularly from Australia."

Russia warned against using aid to enter Ukraine

The United States has warned Russia, meanwhile, that it would be "completely unacceptable" to use the humanitarian crisis in Ukraine as a pretext for an invasion.

The warning comes after Russia proposed setting up humanitarian corridors to come to the aid of civilians in east Ukraine who are fleeing violence as Kiev's forces battle to re-take the main city of Donetsk.

US ambassador Samantha Power told the UN Security Council that international aid agencies were on the ground and helping civilians trapped between pro-Moscow rebels and Ukrainian forces.

"Any further unilateral intervention by Russia in Ukrainian territory, including one under the guise of providing humanitarian aid, would be completely unacceptable and deeply alarming and would be viewed as an invasion of Ukraine," she said.

Moscow proposed that the convoys of aid be organised through the International Committee of the Red Cross (ICRC), but it was unclear how much of a role the ICRC would play in the deliveries.

The United States and other Western countries accuse Russia of backing the separatists fighting Kiev. Moscow denies the charge.

With fighting intensifying near the main city of Donetsk, more civilians are fleeing while those left behind struggle to find water, medical care and other essentials.

UN secretary-general Ban Ki-moon says the UN is ready to boost its support to Ukrainian relief efforts.

Four months of fighting in east Ukraine have left at least 1,300 people dead and driven 285,000 from their homes in a conflict that also brought East-West relations to their lowest point since the end of the Cold War.

Russia's defence ministry overnight said it had finished military exercises in southern Russia which the United States had criticised as a "provocative" step amid the Ukraine crisis.